152 DR WILSON ON THE SOLUBILITY OF 
lain. I endeavoured to substitute for these, silver basins, but found it impossible 
to prevent them gaining weight from the sulphuretted hydrogen constantly pre- 
sent in an analytical laboratory. Through the liberality of Dr Grecory I have 
recently obtained a platina basin of much larger dimensions than the resources of 
my own laboratory afforded, and by means of it I shall be able to announce the 
proportion of fluor-spar taken up by water. Meanwhile, we cannot doubt that 
the proportion of fluorine has hitherto been estimated too low in most of the 
substances ascertained to contain it. In some cases the error must have been 
considerable. 
Thad hoped that the barium salt of fluorine would prove suitable for the 
quantitative estimation of the latter. It certainly would be much better than the 
fluoride of calcium, but according to BERzELius it possesses a certain though 
slight solubility in water. Fluoride of barium must accordingly be rejected also, 
unless no better compound for estimating fluorine quantitatively can be discovered. 
I may remark, in passing, that the fact that fluoride of barium is soluble in water 
might have led to the discovery that the similar salt of calcium was so likewise. 
The salts of barium, as a class, are much more insoluble than those of calcium, 
If, therefore, the barium compound of a salt-radical be soluble in water, the 
calcium salt of the same radical should, a fortiori, be still more so. 
The observation of the previously unsuspected solubility of fluor-spar in 
water, promised to throw light on some interesting problems connected with 
geology, mineralogy, and physiology. I was induced, in consequence, to make a 
series of researches in reference to these points, the results of which I shall now 
briefly state. 
Many of the investigations were very tedious, and I take this opportunity of 
expressing my obligations to two of my pupils, Mr Henry C. Briaes and Mr 
Henry WILLIAM STANSFELD, for the cordial and untiring assiduity with which 
they aided me in my researches. To my assistant, Mr Davip Forpss, I have 
likewise been greatly indebted for the most active co-operation throughout the 
inquiry. 
3. Of the presence of Fluorine m Well, River, and Sea Water. 
It was impossible to doubt, after the facts I had observed in the laboratory, 
that fluorine must be no infrequent constituent of well and river as well as of sea 
water. BERZELIUS mentions that fluoride of calcium has been found in the waters 
of Carlsbad.* Dr Curisrrson has pointed out to me that HuNEFELD detected a 
trace of it in the waters of Gastein in the Tyrol,t and that PLantava found 
or. 0:07 of the fluoride in 10,000 grains of the water of Lukatschowitz in 
* Lehrbuch der Chemie, vol. ii., p. 607. 
+ Bulletin des Sciences Médicales, vol. xvii., 425. From Jahrbuch der Chemie und Physik, xxii. 458, 


